This invention relates to a pushbutton tuner which may be suitably used for a car radio receiver set. More particularly, it relates to such a tuner having the reduced size of its tuning mechanism.
A pushbutton tuning mechanism essentially comprises (a) operative members each having at its one end a pushbutton and positioned for longitudinal movement from an unoperative position to an operative position in response to the depression of its pushbutton, (b) a tuning slider plate responsive to the movement of the operative member for moving in the direction transversely thereof by the amount peculiar to the respective operative member, and (c) tuning determination means responsive to the movement of the tuning slider plate for providing the corresponding mechanical position of the tuning cores with respect to related stationary coils to determine the reception frequency point peculiar to the respective pushbutton.
In general, in order to make the tuning mechanism compact in size, it is a common practice to arrange the operative members horizontally with respect to the plane of the tuner. However, since each of the operative members is, generally, provided with a frequency presetting cam plate pivotally mounted thereon acting to provide a preset amount of movement of the tuning slider plate in cooperation therewith, and a locking plate for fixedly positioning the cam plate at the preset position, it is impossible with such horizontal arrangement of the operative members to provide all pivotal angular positions of the cam plate for the movements of the slider plate corresponding to a sufficient tuning core stroke to cover a desired frequency band, unless there are great distances between the adjacent operative members. Therefore, even though a tuner having the thin size in height is obtainable, the resulting width thereof would become great, so that it is impossible to make the whole size of the tuner compact.
In the prior art, there have been made many kinds of attempts for accomplishing the thinning and compacting of the tuner simultaneously. For example, in U.S. Pat. No. 2,253,433, a pushbutton tuner is shown wherein operative members arranged horizontally with respect to the plane of the tuner are provided therein V-shaped cutouts respectively. As an operative member is depressed from its unoperative position to the operative position, a pin for the respective operative member provided on the slider operatively coupled to a tuning determination mechanism is moved to a point of the related cutout in the operative member, so that said slider carrying the pins is moved transversely of the moving direction of the operative member. The pins respectively engaging the V-shaped cutouts at the front side of the slider are positioned at presettable positions along said front side so that the tuning frequency point selected by the respective pushbutton is freely presettable. The operative member must have at least such a V-shaped cutout width that make possible moving the related pin of the slider by the maximum moving distance of the slider within the rear portion of the V-shaped cutout of the operative member which is in the unoperative position.
This invention provides an improved pushbutton tuner having the reduced size, but without any deterioration of its operation quality by the new structure of the mechanism thereof over the prior art.